import java.util.Scanner;

public class a044_空間切割 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		int n; // 平面 (plane)
		int result; // ( n + 1 ) * ( n^2 - n + 6) / 6
		
		while(sc.hasNext()) {
			n = sc.nextInt();
			
			result = (n + 1) * (int)(Math.pow(n, 2) - n + 6) / 6;
			
			System.out.println(Integer.toString(result));
		}
	}
	
}